Hollywood’s already-crowded summer seemed more packed than usual this weekend, with four new films opening in wide release. But despite a season that’s been good to sequels and franchise fare, it was an original concept sci-fi film that took the top spot at the box office.

“Elysium” edged out competition for the No. 1 spot with a so-so $30.5 million. Three other new movies followed in the next three spots, with “We’re the Millers” opening strong in second place, “Planes” on cruise control in third and “Percy Jackson: Sea of Monsters” floating up fourth.

“Elysium” was a much-anticipated follow-up to director Neill Blomkamp’s “District 9,” which opened in 2009 with $37.4 million and received an Academy Award nomination for best picture. The opening performance of “Elysium” is just average for the $115 million movie co-financed by Sony Corp.’s TriStar Pictures and Media Rights Capital, but international returns for the summer’s last big-budget spectacle should be strong. The sci-fi allegory starring Matt Damon is about a futuristic world in which a majority of humans live on a ruined Earth while the privileged one-percenters live in a utopian space habitat called Elysium.

In second place with $26.6 million was “We’re the Millers,” an R-rated comedy from Time Warner Inc.’s Warner Bros. starring Jason Sudeikis and Jennifer Aniston about a group of strangers who pose as a family to help a marijuana dealer complete a drug deal. With a production budget of only $37 million, the movie is the only new release this weekend considered an excellent opening. The movie opened on Wednesday and had a five-day gross of $38 million.

“Planes” from Walt Disney Co.’s Disneytoon Studios opened in third with $22.5 million. A spinoff of the hugely successful “Cars” franchise developed at Disney’s Pixar Animation Studios, the animated movie stars comedian Dane Cook as the voice of a crop duster that wants to overcome his fear of heights and become a high-flying racer.

The movie’s opening weekend performance is far below the $66.1 million that “Cars 2” grossed in 2011, but “Planes” is insulated from some pressure because it cost only $50 million to produce. The movie was initially developed as a direct-to-DVD release before the studio decided to release it in theaters.

“Percy Jackson: Sea of Monsters” couldn’t repeat the luck seen by many sequels this summer, opening in fourth place to only $14.6 million – less than half what the original Percy Jackson movie opened to in 2010. It also opened on Wednesday and had a five-day gross of $23.5 million. The fantasy adventure movie had a budget of $90 million, and while the franchise has performed better overseas, this weekend’s weak domestic opening calls into question Twentieth Century Fox’s plans for any more installments. Fox is part of Twenty-First Century Fox Inc., and until recently was part of the same company as The Wall Street Journal.